Bowling Green Industrial Academy became part of the Caroline County school system in 1914 when the board of trustees donated the school and land to the Caroline County School Board. The name of the school was changed to Caroline County Training School. George Hays Buchanan was the principal, and Rev. L. L. Davis continued as the agricultural teacher. The school was designed to train teachers for Negro schools.
Although the Caroline County School Board now owned the school, the Sunday School Union remained responsible for operating and supporting the school. The School Board provided the teachers and paid their salaries. The Sunday School Union provided most of the fuel and was solely responsible for all room and board.
During the 1928–1929 school year, Caroline County Training School qualified for accreditation from the Board of Education. The Virginia State Board of Education accredited the school as a high school offering four-year courses in vocational agriculture in 1930, and the name was changed to Union High School.